Technical Field
The present disclosure is directed to chain driven devices, and more particularly to systems and assemblies for driving passenger conveyors.
Description of the Related Art
Conveyor systems, such as moving walkways and escalators, are typically used to help passengers conveniently move from one location to another. The stairways or walkways of passenger conveyors essentially include an interconnected band of pallets, respectively, which are propagated between two landings. The construction of moving walkways for instance typically includes one of two basic styles, either pallet type or moving belt type. A belt type moving walkway typically includes a mesh metal or rubber belt disposed over a series of rollers. A pallet type moving walkway typically includes a continuous series of pallets joined together to form a walkway.
Pallet-type moving walkways generally include a truss assembly which houses a drive mechanism that drives the pallets. Specifically, the pallets are connected to a driving chain that includes a plurality of interconnected rollers. The driving chain is engaged with a drive track and is operatively connected to the drive mechanism, such as one or more drive sprockets. As the drive mechanism drives the driving chain, the pallets move along the drive track from a passenger carrying portion to a return portion, which is typically located underneath the passenger carrying portion. The walkway assembly including the truss assembly, drive mechanism and the return portion is typically located in a pit constructed for that purpose.
In moving walkways employing pit configurations, the height difference between the surrounding floor level and the passenger carrying surface of the pallets, or the pallet height, may sometimes require relatively steep and/or lengthy ramps at the ends of the moving walkway for the purposes of passenger comfort and handicapped access. In addition, parallel moving walkways, operating in opposite directions, would require two pits, two drive mechanisms and two pallet bands, thereby further adding to the overall expense and space requirements of installation. While such concerns have introduced variations of linear drive mechanisms which offer more compact conveyor designs, there is still much room for improvement.
To provide a more compact design, some linear drive systems employ less components and/or smaller components to perform the same tasks required by conventional drive systems. However, this results in a greater magnitude of forces or loads that are exerted on the relatively weaker components, thus increasing wear and reducing sustainability. In other existing linear drive systems, each pallet is directly connected to a set of toothed drive belts or chains which extend the length of several pallets. The flexibility of the lengthy belts or chains, however, results in significant vibrations, which can further lead to increased noise and overall wear on the conveyor.
Still, in other linear drive systems, the drive chains are used to directly engage the pallet rollers. In such configurations, however, the engagement between the drive chain and each pallet roller generates a bending moment on each passing roller. The bending moment not only causes an increase in the wear on the pallet rollers as well as the drive chains, but also reduces the overall efficiency of energy transfer between the drive chains and the pallet rollers. Furthermore, as the drive chains directly engage the pallet rollers, reductions in the pitch length of the drive chains, and thus reductions in the overall height of the conveyor system, are constrained by the size of the pallet rollers.
Thus, there is a need for a more compact drive system that can provide for an overall shallower passenger conveyor design and realize pit-free conveyor implementations. Moreover, there is a need for a moving walkway with reduced passenger carrying surface height relative to the surrounding floor surface for improved passenger comfort, easier handicapped access, as well as better aesthetics of the landing design. There is also a need for a more reliable drive system which operates with less noise and less vibrations. In particular, there is a need for a drive system which transfers the rotational torque, or the force generated by a drive machine, into translational movement of the pallets with more efficiency, while reducing the wear on the individual components thereof.